Saw chain



Feb. 9, 1960 A. GUDMUNDSEN .v 2,924,110 SAW CHAIN I I Filed Aug. 20. 1956 INVENTOR, AUSTIN GUDMU/VDSE/V.

SAW CHAIN Austin Gudmundsen, Inglewood, Califi, assignor to McCulloch Corporafion, Los Angeles, Calif., a corporation of Wisconsin Application August 20, 1956, Serial No. 605,047

Claims. (Cl. 74-245) This invention relates to saw chains of the type which are operated along the grooved edge of a fiat bar, and relates in particular to a saw chain having reduced liability of link breakage.

The conventional saw chain includes center links and side links articulated by pintles. The center links have projections which enter the groove in the bar edge and the side links slide along the edges or rails which lie on opposite sides of the groove. There has been a previously unexplained rupture of the side links along transverse lines extending substantially centrally through the pintle openings. This breakage has become a problem because it renders the saw chain inoperative until repair is made.

The present invention solves this problem and substantially eliminates the breakage referred to in the foregoing. I have discovered the cause of this breakage and the present invention eliminates this cause. The side links of conventional chains are punched from a sheet of steel, the result being that the bar-confronting edge surfaces are rough. When the saw chain is first run upon the saw bar localized overheating of the metal occurs at the rough high spots lying adjacent the pintle openings, producing small patches of hard brittle steel and minute thermal stress cracks. Where these cracks are in a stressed area, for example, the area between the pintle opening and the bar-confronting edge, rupture will occur along a line extending from the pintle opening to the edge and the end of portion of the side link will break ofi.

It is an object of the present invention to initially form the bar-confronting edge of the side links so that the initial points of contact with the bar rail, both in the main body portion of the bar and around the curved end thereof, are offset from the transverse center lines through the pintle openings as far as possible, or at least to such an extent that the zones of initial overheating of the side link edges will be well to one side or the other of the pintle opening.

It is an object of the invention to provide a side link for a saw chain wherein the bar-confronting edge of the link has protuberances which are offset from the transverse center lines of the pintle openings.

It is a further object of the invention'to provide a chain link of the character set forth in the preceding paragraph wherein these protuberances are produced by shearing the bar-confronting edge of each side link at a slight angle from the link ends toward the mid portion, so that when the link is traveling across the main straightaway portion of the bar, only the extreme end portions of the link, displaced from the transverse center lines of the rivet holes, initially contact the rails. The result of this is that any stress cracks resulting from localized overheating will be in a region outside the load stressed area of the link. Also, as the chain travels around the curved bar end, the side links make contact with the ited States Patent 0 Patented Feb. 5, 1960 curved bar edges of lesser radius at points adjacent the mid-portion of the link.

Further objects and advantages of the invention may be brought out in the following part of the specification wherein some details have been described for the purpose of competence of disclosure without intending, however, to limit the scope of the invention which is defined by the accompanying claims.

Referring to the accompanying drawings which are for illustrative purposes only,

Fig. l is an enlarged fragmentary elevational view of a portion of a chain embodying the present invention and a portion of a saw bar edge;

Fig. 2 is a sectional view taken substantially as indicated by the line 22 of Fig. 1; v

Fig. 3 is a schematic view showing the relative position of a side link and the curved end of a saw bar; and

Fig. 4 is a face view of an alternative side link embodying the invention.

In Figs. 1 and 2 a portion of a saw bar 10 is shown. In its edge portion it has a longitudinal groove 11 and parallel edges or rails 12 lying on opposite sides of the groove. The chain which operates on the bar 10 comprises center links 13 and side links 14. Some of the links carry cutters thereon. The cutters may be on the center links or the side links. In the present disclosure I show a cutter 15 on one of the side links 14. It will be understood that the chain employs a plurality of such cutters in allochiral relation.

The side links 14 are connected to the center links 13 by pintles 16 which extend through pintle openings 17 in the center links and relatively smaller pintle openings 18 in the side links. The pintles 16 have cylindrical portions 19 which occupy and are turnable within the pintle openings 17 of the center links 13, and coaxial stems 20 which extend outwardly through the pintle openings 18 of the side links 14. The stems 20 of the pintles 16 are locked in the pintle openings 18 so that the pintles do not rotate relatively to the side links 14 but do rotate in the pintle openings 17 of the center links. This non-rotative connection of the pintles 16 with the side links 14 is accomplished by radially expanding the stems 20 within the pintle openings 18 and then fianging the outer ends of the stems 20 by riveting action so as to produce flat rivet heads 21 thereon.

Each center link 13 has an extension 22 which runs in the bar groove 11, and each side link 14 has a barconfronting edge portion 23 which slides along a bar edge or rail 12. This bar-confronting edge portion 23 of each side link 14 has therein a centralized depression or shallow notch 24, and at its ends the bar-confronting edge portion 23 has protuberances 25 for engagement with the rails or edges 12 of the bar It The term 4 protuberance is intended to mean a portionof the link 14, such as indicated at 25, for example, which protrudes barward from the longitudinal center lines cc a greater distance D than the distance d of the link edge portion 26 which lies adjacent the protuberance 25. In the preferred form of the invention shown, the protuberances 25 are formed by cutting the edges 27 of the link 14 which lie on opposite sides of the notch 24, in non-parallel relation to the center line c-c. These edges 27 are cut at an angle a to the edge 12 which is approximately parallel to the center line cc.

When the chain is initially used upon the bar 10, the areas of localized heating occur as indicated by the dotted lines h. These areas h are materially offset from the areas of minimum cross-section of the links 14 which coincide with the transverse center lines tt which intersect the axes of the openings 18, and the minute cracks which may occur in the areas of localized overheating h of the protub'erances 25 will not result in rupture of the chain links through the pintle opening 18 thereof.

In Fig. 3, I show a side link 14 resting against the curved edge 120 of the saw barltl. At this time the points of engagement 28 of the'bar edgelZc and the barconfronting edge portion 23 of'the link 14"a'reo'ffset from" the transverse center "lines tt of the'pintle openings 18 toward 'the mid-'po'rtionof the link 14. Therefore, any localized overheating which" rn'ayo'ccur in' the proximity of the points 28 cannot result"in'c'hain link rupture.

In Fig.4, I show an-alternative method of forming protuberances lifl on'the bar-confrontingedgesof a link 14'. Instead of providing a-link'with diagonal edges t such as shown at 27 'in Fig. 1, 'd'epre's'sions'31 are formed in the link edges opposite'the'pintlejopenings'18, thereby. providing the protuber'anc'es "30 at the ends of the depressions 31' and inoff'set relation to the transverse center lines of the pintle openings 18.

I claim:

1. A saw chain for a"sawingdevice'havingasaw bar 'with a peripheral 'groove therein, side edges and rounded end edges upon which the side linksof the saw chain are adapted to slide, comprising: center links with extensions adapted to slide in the peripheral grooveof the bar; side links with bar confronting edges, said sidelinks having pintle openings near the ends thereofyand' pintlesconnecting the side links to the center links, said side links having protuberances at substantially the extreme end portions thereof constituting initial points of contact with groove therein, side edges and rounded end edges; a

chain saw having center links-with extensions slidable in the peripheral groove of the bar; side links with bar confronting edges, said side linkshavingpintle openings near the ends thereof; andpintles' connecting the side links to the center links, said side links having contact points at substantially the extreme end portions of said bar confronting edges'constituting points of contact with the side edgesof said saw bar and other points ofcontact with the rounded bar edges of lesser radius at-points adjacent the mid-portion of the links, said points of contact being offset from the axes of the pintleopenings longitudinally relative to the links andoutside theload stressed areas ofthe links.

' 3; A-saw chain for a sawing devicehaving a'saw bar with a peripheral groove-therein, side edges and rounded end edges upon which the 'side links of the saw chain are adapted to slide, comprising? center links with extensions adapted toslide in the peripheral groove of the bar; side links with bar confronting edges, said side links having pintle openings near the-ends thereof; and pintles connecting the sidelinks tothecenter links,-said bar-confronting edges including portions extending inwardly from adjacent the link ends and inclined upwardly in a-direction toward the longitudinal axes of the links to provide protuberances at substantially the extreme end portions of said bar confronting edges constituting initial points of contact with the side edges of said saw bar in the main body portion of the bar and other points of contact with the rounded bar edges of lesser radius at points adjacent the mid-portion of links, said initial points of contact being offset from the axes of the pintle openings longitudinally relative to the links to such an extent that the zones of initial overheating of the side link edges are relatively remote from. the pintle openings in a region outside the load stressed areas of the links.

4. A saw chain for a sawing device having a saw bar with a peripheral .groove therein, side edges and rounded end edges upon "which' the side links of the saw chain are adapted to'.slide,comprising: center links with extensions adapted to slide in the peripheral groove of the bar; side links with bar confronting edges, said side links having pintle openings near the ends thereof; and pintles connecting the side links-to the center-links, said side links having spaced along the bar confronting edges thereof a depressiondisposed adjacenteachend of said side links with each depression having'the center thereof opposite one of said pintleopenings, the portions of said side link bar confronting edges extending outwardly atthe endsof said depressions-providing protuberances at substantially the extreme: end portions of said bar confronting'edges' constitutinginitial points ofcontact with the side edges of said saw bar in=the:main bodyportion of thebanand other pointsof contachwith the rounded bar edges of lesser radius at points adjacentthe mid-portion ofthe links;said initi'ai points of contact. being offset from the axes of the pintle openings longitudinally relativetothe links tosuch an extentlthat. the zones of initial overheating of the side link edges: are relatively remote from the pintle openings. in a .regionuoutside thelload stressed'areas of the links.

5. A sawchain for asawingdevicehaving a. saw bar -with a peripheral groove therein,x.side. edges and rounded end edges upon which the side :links of the sawtchain are adapted to slide,'comprising: center links with extensions adapted to slide in zthe peripheral groove of the bar; side links: with bar. confronting edges, said side links having pintle. openings near the ends thereof; and pintles connecting. the side links to the center links, said side links having bar-engaging'edge portions at substantially the extreme end portions of said sidelinks for frictional engagement with the side. edges of said saw. barin the main portion of the bar, and other bar-engagingledge portions for frictionalengagementwiththe rounded bar edges of lesser radius at pointsadjacen't the mid-portion of said links, said first named bar-engaging edge portions being offset from the axes of thepintle openings longitudinally relative to the links to such an extent that the zones of initial overheating of the side linkedges are relatively remote from the pintle openings in a region outside'the' loadstressed areas of the links.

References Citedin the file of thisupatent UNITED STATES PATENTS 1 Great Britain of 1904 

